1. Field of the Invention
The present invention relates to a circuit arrangement for telecommunications systems and is particularly concerned with telephone switching systems which comprise information interrogating devices cyclically driving a plurality of inquiry locations. The information interrogating devices solicit information which may be present with different interrogation frequencies with respect to the various inquiry locations and modify the interrogation frequency with respect to a respective inquiry location depending on the appearance of an information to be called in. Interrogation memories assigned to the information interrogating devices in which the individual plurality of selection events within an overall control cycle respectively covering all inquiry locations are individually stored for each of the inquiry locations, whereby the individual plurality of selection events is stored in the interrogation memory for each of the inquiry locations by way of a corresponding one-time or repeated storing of their respective addresses at a corresponding number of memory locations which are distributed within the cycle sequence of the totality of the memory locations being particularly regularly distributed and being successively cyclically read.
2. Description of the Prior Art
A circuit arrangement of this type is disclosed in the German published application No. 3,443,616 and enables inquiry locations to be interrogated with differing frequency. Inquiry locations can be individual scan points, for example in subscriber-associated switching devices such as connector sets or subscriber line circuits. This is set forth in greater detail in, for example, the German published application 2,748,795 which, with the aforementioned German published application is fully incorporated herein by this reference. Incoming switch identifiers are recognized in that different interrogation results are acquired in the interrogation events undertaken at a scan point proceeding from a certain time than are acquired before that time, namely for the duration of the switch identifier. In this context, the latter-mentioned application discloses that, for example, selection pulses output from subscriber stations arrive in connector sets. The scan points are normally scanned at a relatively slow tempo. When the beginning of the selection pulse is recognized by way of an interrogation event, then the relatively slow interrogation tempo is replaced by a relatively fast interrogation tempo. In an arrangement as disclosed in this published application, the possibility is provided of chronologically acquiring the end of a respective selection pulse as accurately as possible and, therefore, the duration of the appertaining dial pulse. In this manner, for example, selection pulses and switch identifiers formed by these pulses having a different duration can be distinguished from one another with great reliability.
When an interrogation result indicating a pulse beginning is identified in this latter known instance, then the interrogation tempo having a relatively low sequence changes to one having a relatively fast sequence. When, in the second interrogation event (or in the third interrogation event), a further interrogation result of the same content is identified after an interrogation result indicating a pulse beginning, then it is perceived that it was, in fact, not a matter of a pulse beginning, but a matter of a disturbance. In response thereto, the interrogation rhythm for the further interrogation events is changed back from the relatively fast sequence to the relatively slow sequence.
As is known from the mentioned German published application No. 2,748,795, the change of the interrogation tempo serves the purpose of increasing the interrogation capacity of an interrogating device by slowing the interrogation tempo in that the number of inquiry locations can be likewise increased to a corresponding degree, whereby a chronologically relatively exact acquisition of switch identifiers having a specific and individual duration is nonetheless guaranteed. When, however, it is not a matter of cyclical scanning of scan points for the acquisition of switch identifiers by distinguishing the switch identifier condition from the switch condition alternative thereto (for example pulse pause and "interselection time"), but is a matter of a call-in of complete information from individual inquiry locations, then a different problem arises. The volume of information to be called in can differ greatly at different inquiry locations. When the different inquiry locations are uniformly cyclically selected, then there can be inquiry locations where the information to be called in back up, whereas there are other inquiry locations at which information for call in are only sporadically present when they are selected and interrogated. In comparison to the principle of cyclic scanning, the principle is also known in this context of selecting inquiry locations on the basis of individually output request signals. What is disadvantageous, however, is the outlay which must be expended for generating, emitting, transmitting, accepting and evaluating these request signals, as well as the successive processing of the request signals. The invention therefore proceeds from the circuit arrangement of the type mentioned above wherein the various inquiry locations are cyclically selected.
It can occur in circuit arrangements of the type set forth above that the volume of information to be called in is not only unequal at the various locations, but is also subject to fluctuations, per inquiry location, and that a discontinuous change of the crush of information to be called in can occur at the individual inquiry locations. In order to counter this problem, the aforementioned German published application No. 3,443,616 has proposed a circuit arrangement in which it is provided that an information interrogating device executing successive interrogation cycles assigns cycle numbers to the inquiry locations and stores them for the assignment of interrogation frequencies for the inquiry locations. These cycle numbers indicate the respective number of interrogation cycles at which the appertaining inquiry location is selected each time. Accordingly, an inquiry location is interrogated only once in an interrogation cycle or in two or more interrogation cycles, in particular based on the measure of a respectively stored cycle number. It is also proposed in accordance with the circuit arrangement that the information interrogating device immediately selects an inquiry location in the next interrogation cycle each time an information from this inquiry location has been received and either repeats this given renewed receipt of an information and, in the opposite case, again continues the interrogation tempo from this point on based on the measure of the cycle numbers stored for this inquiry location. Accordingly, therefore, the interrogation tempo per inquiry location is boosted from an interrogation tempo individually assigned to the appertaining inquiry location to a uniform, maximum interrogation tempo. In addition, the mentioned proposed circuit arrangement provides that the information accepted from the various inquiry locations are counted in time intervals per inquiry location and the cycle numbers are again adapted after each time interval, being adapted inversely proportional based on the measure of these counter results, for example by the respective value "1". In accordance therewith, therefore, the cycle numbers stored for inquiry location are dynamically adapted based on the actual traffic volume.
In a circuit arrangement of this type, therefore, a great crush of information to be called in at an inquiry location effects that this is not interrogated based on the measure of the respectively stored cycle number, but is interrogated in every interrogation cycle. This means that the inquiry locations having the currently-heaviest volume of information to be interrogated are interrogated with equal frequency. A greater crush of information to be interrogated at all inquiry locations would result in the fact that all inquiry locations would be interrogated with identical frequency. As a result thereof, the effect produced by the cycle numbers stored per inquiry location, namely that the various inquiry locations are interrogated with different frequencies, would be completely leveled precisely in those times having a particularly heavy volume of information to be interrogated.